Molecular characterization of inversion breakpoints in the Drosophila nasuta species group

Chromosomal inversions are fundamental drivers of genome evolution. In the Drosophila genus, inversions have been widely characterized cytologically, and play an important role in local adaptation. Here, we characterize chromosomal inversions in the Drosophila nasuta species group using chromosome-level, reference-quality assemblies of seven species and subspecies in this clade. Reconstruction of ancestral karyotypes allowed us to infer the order in which the 22 identified inversions occurred along the phylogeny. We found a higher rate of inversions on the X chromosome, and heterogeneity in the rate of accumulation across the phylogeny. We molecularly characterize the breakpoints of six autosomal inversions, and found that repeated sequences are associated with inversion breakpoints in four of these inversions, suggesting that ectopic recombination is an important mechanism in generating inversion. Characterization of inversions in this species group provides a foundation for future population genetic and functional studies in this recently diverged species group.